Limiters can be used to prevent damage caused to circuits, such as microwave circuits. For example, if a receiver is very sensitive to what it can hear far away, it can be easily damaged by high power signals. Limiters can prevent sensitive circuitry from high power signals by, for example, attenuating high power signals to prevent this damage. Currently, many limiters are wide bandwidth, so if a very narrow band high power signals is received, many conventional limiters attenuate all signals that are received by a circuit, and no information (in any frequency) is received after this attenuation.
Switched multiplexers can be used in radio frequency (RF) and microwave systems to separate and re-join frequency bands for more-optimal analysis of signals. Their switching capability can allow the selection of which bands will be passed and which bands to be highly attenuated. Three of the most important performance metrics for switched multiplexers are insertion loss, group delay ripple, and high power signal limiting capability.
Switched multiplexers are typically implemented by splitting the input signal into even- and odd-numbered channels (which gives an inherent architecture loss) or with the use of nonreciprocal devices such as amplifiers (which adds noise to the circuit) to prevent the switching of channels from affecting the response of adjacent channels. In passive switched multiplexer designs without amplifiers, the architecture-related loss and the dissipative losses of the couplers, switches, and power dividers often results in passband insertion losses greater than 10 dB. The group-delay ripple in conventional switched multiplexers tends to be quite high, even in so-called flat group-delay designs.
Features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.